ToF Sensor Pixel Charge Drainage for Distance Ambiguity
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Solution Overview
Problem
Conventional Continuous Wave (CW) ToF sensors face a distance ambiguity problem, requiring additional power and measurements to resolve, which is not always necessary as the scene may not contain objects at longer distances.
Innovation Solution
A ToF sensor with a plurality of photo-sensitive sensor pixels, each comprising at least two charge storages and a drain terminal, where a common charge storage is coupled to the drain terminal of a subset of these pixels, allowing for selective drainage and storage of charge carriers generated by incident light, with the common charge storage accumulating electrical energy indicative of objects outside the target measurement range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional measurements are performed to resolve distance ambiguity, then measurement precision is improved, but use of energy increases and productivity decreases
Solution Approach 1:
The patent applies partial action by performing measurements selectively - only when distance ambiguity is detected. The system first performs a standard ToF measurement, and only if ambiguity is present does it perform additional measurements with different modulation frequencies. This avoids unnecessary energy consumption while maintaining measurement precision when needed.
Solution Approach 2:
The system uses its own measurement data to determine whether additional measurements are needed. By analyzing the correlation function and detecting ambiguity in the initial measurement, the system self-regulates the measurement process, performing additional measurements only when the data indicates ambiguity is present.
2Measurement precision
If additional measurements are performed to resolve distance ambiguity, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The system performs partial measurements - only the necessary number of measurements to resolve ambiguity. By using the correlation function analysis to detect ambiguity, the system avoids performing full sets of additional measurements when they are not needed, thus maintaining productivity while ensuring precision when required.
Solution Approach 2:
The system uses feedback from the initial measurement (correlation function analysis) to control whether additional measurements are performed. The measurement process is adaptive - the result of the first measurement determines the need for subsequent measurements, optimizing the balance between precision and productivity.
3Measurement precision
If a common charge storage is added to drain charge carriers from multiple pixels, then device complexity increases, but measurement precision improves
Solution Approach 1:
The patent merges the charge storage functionality across multiple pixels by introducing a common charge storage that receives charge carriers from multiple pixel units. This consolidation allows shared processing of charge data to detect distance ambiguity, improving measurement precision while the modular design keeps the added complexity manageable.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables efficient determination of objects outside the target measurement range, reducing unnecessary measurements and power consumption while maintaining accurate distance measurements within the range.
Implementation Method 1
A pixel comprising the photo electric conversion element is equipped with plural capacitors
Implementation Method 2
The common charge storage comprises one or more capacitor or potential well formed in a semiconductor material
Data Source
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AI summary
A Time-of-Flight (ToF) sensor is provided. The ToF sensor includes a plurality of photo-sensitive sensor pixels each comprising at least two charge storages and a drain terminal. Further, the ToF sensor includes a common charge storage coupled to the respective drain terminal of at least a first subset of the plurality of photo-sensitive sensor pixels. For at least one of a plurality of first ToF measurements, the photo-sensitive sensor pixels of at least the first subset are configured to, via the respective drain terminal, drain part of charge carriers generated in the respective photo-sensitive sensor pixel during the at least one of the plurality of first ToF measurements by incident light caused by one or more object outside a target measurement range of the ToF sensor. Further, for the at least one of the plurality of first ToF measurements, the photo-sensitive sensor pixels of at least the first subset are configured to selectively store another part of the charge carriers in the at least two charge storages of the respective photo-sensitive sensor pixel. The common charge storage is configured to accumulate electrical energy conveyed by currents output by the coupled drain terminals and output first data indicative of the accumulated electrical energy.